This has been happening for the last week for me as well. At first, I thought it was bandwidth, but it's just getting worse and I've ruled the bandwidth problem out. I have an iPad (3rd Gen) and I'm trying to watch video streaming from the iTunes store (Warehouse 13, if you care). When it begins to bork and stutter the video, audio keeps rolling along fine. I can usually pause or exit, kill Video, reopen Video and get it to work again for 5-10 minutes.
And then after a couple days of this, downloaded video began to do the same things. Then last night, saved video crashed the entire OS twice - and this is after I ran the sucessfully ran the OS update that had been waiting for a copule of weeks.
This is really ******* me off. I pay for the Apple platform because I expect the software & media FROM APPLE to Just Work.